Reland 8636: Implement setting the length property for FixedDoubleArrays.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index b1d5f1453c1a6aa62e760db7df455dc3a6aa1da2..8e2843597f653a96649174d11b19bdfe48d54e52 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -3207,7 +3207,7 @@ MaybeObject* JSObject::DeleteElement(uint32_t index, DeleteMode mode) {
     case FAST_DOUBLE_ELEMENTS: {
       int length = IsJSArray()
           ? Smi::cast(JSArray::cast(this)->length())->value()
-          : FixedArray::cast(elements())->length();
+          : FixedDoubleArray::cast(elements())->length();
       if (index < static_cast<uint32_t>(length)) {
         FixedDoubleArray::cast(elements())->set_the_hole(index);
       }
@@ -7627,32 +7627,57 @@ MaybeObject* JSObject::SetElementsLength(Object* len) {
   if (maybe_smi_length->ToObject(&smi_length) && smi_length->IsSmi()) {
     const int value = Smi::cast(smi_length)->value();
     if (value < 0) return ArrayLengthRangeError(GetHeap());
-    switch (GetElementsKind()) {
-      case FAST_ELEMENTS: {
-        int old_capacity = FixedArray::cast(elements())->length();
+    JSObject::ElementsKind elements_kind = GetElementsKind();
+    switch (elements_kind) {
+      case FAST_ELEMENTS:
+      case FAST_DOUBLE_ELEMENTS: {
+        int old_capacity = FixedArrayBase::cast(elements())->length();
         if (value <= old_capacity) {
           if (IsJSArray()) {
             Object* obj;
-            { MaybeObject* maybe_obj = EnsureWritableFastElements();
+            if (elements_kind == FAST_ELEMENTS) {
+              MaybeObject* maybe_obj = EnsureWritableFastElements();
               if (!maybe_obj->ToObject(&obj)) return maybe_obj;
             }
-            FixedArray* fast_elements = FixedArray::cast(elements());
             if (2 * value <= old_capacity) {
               // If more than half the elements won't be used, trim the array.
               if (value == 0) {
                 initialize_elements();
               } else {
-                fast_elements->set_length(value);
-                Address filler_start = fast_elements->address() +
-                                       FixedArray::OffsetOfElementAt(value);
-                int filler_size = (old_capacity - value) * kPointerSize;
+                Address filler_start;
+                int filler_size;
+                if (GetElementsKind() == FAST_ELEMENTS) {
+                  FixedArray* fast_elements = FixedArray::cast(elements());
+                  fast_elements->set_length(value);
+                  filler_start = fast_elements->address() +
+                      FixedArray::OffsetOfElementAt(value);
+                  filler_size = (old_capacity - value) * kPointerSize;
+                } else {
+                  ASSERT(GetElementsKind() == FAST_DOUBLE_ELEMENTS);
+                  FixedDoubleArray* fast_double_elements =
+                      FixedDoubleArray::cast(elements());
+                  fast_double_elements->set_length(value);
+                  filler_start = fast_double_elements->address() +
+                      FixedDoubleArray::OffsetOfElementAt(value);
+                  filler_size = (old_capacity - value) * kDoubleSize;
+                }
                 GetHeap()->CreateFillerObjectAt(filler_start, filler_size);
               }
             } else {
               // Otherwise, fill the unused tail with holes.
               int old_length = FastD2I(JSArray::cast(this)->length()->Number());
-              for (int i = value; i < old_length; i++) {
-                fast_elements->set_the_hole(i);
+              if (GetElementsKind() == FAST_ELEMENTS) {
+                FixedArray* fast_elements = FixedArray::cast(elements());
+                for (int i = value; i < old_length; i++) {
+                  fast_elements->set_the_hole(i);
+                }
+              } else {
+                ASSERT(GetElementsKind() == FAST_DOUBLE_ELEMENTS);
+                FixedDoubleArray* fast_double_elements =
+                    FixedDoubleArray::cast(elements());
+                for (int i = value; i < old_length; i++) {
+                  fast_double_elements->set_the_hole(i);
+                }
               }
             }
             JSArray::cast(this)->set_length(Smi::cast(smi_length));
@@ -7663,8 +7688,14 @@ MaybeObject* JSObject::SetElementsLength(Object* len) {
         int new_capacity = value > min ? value : min;
         if (new_capacity <= kMaxFastElementsLength ||
             !ShouldConvertToSlowElements(new_capacity)) {
-          MaybeObject* result =
-              SetFastElementsCapacityAndLength(new_capacity, value);
+          MaybeObject* result;
+          if (GetElementsKind() == FAST_ELEMENTS) {
+            result = SetFastElementsCapacityAndLength(new_capacity, value);
+          }  else {
+            ASSERT(GetElementsKind() == FAST_DOUBLE_ELEMENTS);
+            result = SetFastDoubleElementsCapacityAndLength(new_capacity,
+                                                            value);
+          }
           if (result->IsFailure()) return result;
           return this;
         }
@@ -7700,7 +7731,6 @@ MaybeObject* JSObject::SetElementsLength(Object* len) {
       case EXTERNAL_FLOAT_ELEMENTS:
       case EXTERNAL_DOUBLE_ELEMENTS:
       case EXTERNAL_PIXEL_ELEMENTS:
-      case FAST_DOUBLE_ELEMENTS:
         UNREACHABLE();
         break;
     }